basic: can now execute user apps!

Shell replacement sequence beginning in 3, 2, 1...

apps/basic/README.md

@@ -227,3 +227,9 @@ device (bseek, getb, putb).
 **ldbas <fname>**: loads the content of the file specified in the argument
 (as an unquoted filename) and replace the current code listing with this
 contents. Any line not starting with a number is ignored (not an error).
+
+**basPgmHook**: That is not a command, but a routine to hook into
+`BAS_FINDHOOK`. If you do, whenever a command name isn't found, the filesystem
+is iterated to see if it finds a file with the same name. If it does, it loads
+its contents at `USER_CODE` (from `user.h`) and calls that address, with HL
+pointing to the the remaining args in the command line.

apps/basic/fs.asm

@@ -77,6 +77,29 @@ basFOPEN:
 	push	de \ pop ix	; IX now points to the file handle.
 	jp	fsOpen
 
+basPgmHook:
+	; Cmd to find is in (DE)
+	ex	de, hl
+	; (HL) is suitable for a direct fsFindFN call
+	call	fsFindFN
+	ret	nz
+	; We have a file! Let's load it in memory
+	ld	ix, BFS_FILE_HDL
+	call	fsOpen
+	ld	hl, 0		; addr that we read in file handle
+	ld	de, USER_CODE	; addr in mem we write to
+.loop:
+	call	fsGetB		; we use Z at end of loop
+	ld	(de), a		; Z preserved
+	inc	hl		; Z preserved in 16-bit
+	inc	de		; Z preserved in 16-bit
+	jr	z, .loop
+	; Ready to jump. Return USER_CODE in IX and basCallCmd will take care
+	; of setting (HL) to the arg string.
+	ld	ix, USER_CODE
+	cp	a		; ensure Z
+	ret
+
 basFSCmds:
 	.dw	basFLS
 	.db	"fls", 0, 0, 0

tools/emul/bshell/glue.asm

@@ -3,6 +3,7 @@
 .inc "err.h"
 .inc "ascii.h"
 .equ	RAMSTART	0x4000
+.equ	USER_CODE	0x4200
 .equ	STDIO_PORT	0x00
 .equ	FS_DATA_PORT	0x01
 .equ	FS_ADDR_PORT	0x02
@@ -109,7 +110,9 @@ basFindCmdExtra:
 	call	basFindCmd
 	ret	z
 	ld	hl, basBLKCmds
-	jp	basFindCmd
+	call	basFindCmd
+	ret	z
+	jp	basPgmHook
 
 emulGetC:
 	; Blocks until a char is returned

tools/emul/bshell/user.h

@@ -1,5 +1,5 @@
 .equ    SHELL_RAMSTART  0x4100
-.equ    USER_CODE       0x4200
+.equ    USER_CODE       0x4200  ; in sync with glue.asm
 
 ; *** JUMP TABLE ***
 .equ	strncmp			0x03